This invention relates to the field of orthodontics, and in particular it concerns improvements relating to the type of retainer adapted to locate a wire against the labial surfaces of the upper or lower anterior teeth, which retainer is commonly referred to as a "Hawley Retainer".
In the overall process of effecting straightening of a child's teeth, a point is reached at which the teeth themselves have been completely straightened, whereupon the straightening appliances such as braces or the like are removed and a retainer such as a Hawley Retainer is utilized for urging the straightened teeth into a final position. At the present time, the procedure for making this retainer is as follows. Firstly, an impression of the teeth is made, from which is molded a plaster of paris model of the patient's teeth. A wire is then shaped and adapted to the model. The model is then coated with a separating medium and the wire is glued to the model. A self-cure acrylic methyl methacrylate acrylic is then poured onto the model to the correct thickness. The retainer is then removed from the model, cleaned, and trimmed ready to be fitted to the patient's mouth. The retainer is then fitted to the mouth and the bite plane is adjusted to the correct position and then polished.
In an alternative, and in some ways more complicated procedure, instead of using the self-cure acrylic, a flat disc is either drawn by suction or pushed by fluid pressure onto the model of the patient's teeth. All suction procedures require the added complication of providing a suction means for cooperating therewith while some suction processes require the added complication of drilling suction holes through the model. The pressure procedures require the further complication of fixing the wire in place with self-cure acrylic so that it is not displaced during the forming process. In either event, forming such a custom retainer is quite time consuming in that it requires one to one and a half hours, approximately half of which is the orthodontists actual time, the other half comprising lab time. However, of perhaps greater significance is the fact that because of various other delays such as the time required for drying of the cast, it takes at least several days between the time that the orthodontic appliances are removed and the time that the completely fabricated custom made retainer can first be used. This represents a considerable disadvantage since relapse occurs almost immediately upon removal of the straightening appliances. It has been found for example that almost 30% of the relapses in overbite and overjet of finished cases occur within the first ten days following band removal. Hence, this delay of several days between band removal and the commencement of retainer use provides a significant opportunity for this type of relapse to occur. There is also psychological disadvantages resulting from this delay of several days in that the cooperation enthusiasm of the patient may well diminish during this delay while waiting for a custom retainer with nothing to wear in his mouth during this time.
Hence, there exists a need for improvements relating to a retainer of the type described which will reduce or eliminate the disadvantages existing in the present state of the art.